Camera using beam splitter with micro-lens image amplification

ABSTRACT

In one aspect, an imaging system is provided. The imaging system has a taking lens unit adapted to focus light from a scene, and a beam splitter receiving light from the scene with a portion of the received light traveling from the beam splitter to a first imaging surface and a portion of the received light traveling from the beam splitter to a second imaging surface. A first image capture system is provided for capturing an image based upon the light traveling to the first imaging surface, and a second image capture system is provided for capturing a second image based upon the image formed at the second imaging surface. An array of micro-lenses is in optical association with the first imaging surface, with each micro-lens in the array concentrating a first fraction of the light from the beam splitter onto concentrated image areas of the first imaging surface. Wherein the first image capture system forms an image based upon the light concentrated onto the concentrated image areas.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to a group of seven previously co-filed andcommonly assigned U.S. Patent Applications, namely U.S. patentapplication Ser. No. 10/170,607, entitled Camera Speed Color Film WithBase Side Micro-Lenses, filed in the name of Irving et al. on Jun. 12,2002; U.S. patent application Ser. No. 10/171,012, entitled LenticularImaging With Incorporated Beads, filed in the name of Chari et al. onJun. 12, 2002; U.S. patent application Ser. No. 10/167,746, entitledCamera Speed Color Film With Emulsion Side Micro-Lenses, filed in thename of Szajewski et al. on Jun. 12, 2002; U.S. patent application Ser.No. 10/167,794, entitled Imaging Using Silver Halide Films WithMicro-Lens Capture, And Optical Reconstruction, filed in the name ofIrving et al. on Jun. 12, 2002; U.S. patent application Ser. No.10/170,148, entitled Imaging Using Silver Halide Films With Micro-LensCapture, Scanning And Digital Reconstruction, filed in the name ofSzajewski et al. on Jun. 12, 2002; U.S. patent application Ser. No.10/281,654, entitled Imaging Using Silver Halide Films With InverseMounted Micro-Lens And Spacer, filed in the name of Szajewski on Oct.28, 2002, and U.S. patent application Ser. No. 10/326,455, entitledImaging System Having Extended Useful Latitude, filed in the name ofSzajewski et al. on Dec. 20, 2002, the contents of which areincorporated herein by reference.

FIELD OF THE INVENTION

This invention is related to hybrid and combination imaging systemshaving beam splitters.

BACKGROUND OF THE INVENTION

Hybrid and combination imaging systems are designed to capture an imageof a scene using more than one image capture system. This can be donefor a variety of purposes. Often hybrid and combination imaging systemsare used to capture images of the same scene using different types ofimage capture systems.

Such hybrid cameras often use a single taking lens system to collect andfocus light from the scene. In such cameras, a beam splitter is used todeliver the same scene image from the taking lens system to separateimaging surfaces in the hybrid or combination camera. The use of beamsplitters in cameras having more than one imaging surface has also beenknown since at least the inception of the “Technicolor” image separationtechnique for silver halide color image capture in the early-20^(th)century. In the “Technicolor” technique, beam splitters are employed inconjunction with color filters to enable simultaneous capture of colorseparation images on monochrome film stock. More recently, beamsplitters have been proposed for color separation image capture indigital cameras using color filters and monochrome solid state imagecapture devices.

Other examples of hybrid and combination camera systems that use beamsplitters include JP Pat. Pub. No. 10142685A entitled “Silver SaltPhotographic and Electronic Image Pickup Camera” filed by Atsushi onNov. 11, 1996 and J.P. Pat. Pub. No. 11231372, entitled “Camera ProvidedWith Preview Function” filed by Toru on Feb. 17, 1998 each describehybrid film/electronic image capture systems having a main taking lenssystem with a beam splitter that deflects a portion of the lighttraveling through the taking lens system onto an electronic imagecapture surface and permits another portion of the light passing throughthe beam splitter to strike a photosensitive film. Beam splitters havealso found other uses in hybrid cameras. For example, the KodakAdvantix™ Preview™ camera sold by Eastman Kodak Company, Rochester, N.Y.uses a beam splitter to divide light between one path leading to anoptical viewfinder system and another path leading to an electronicimager.

One drawback of the use of such beam splitting systems is that sharingthe light captured by a taking lens system to form images at differentimaging surfaces inherently reduces the amount of light available ateach imaging surface during the time allotted for image capture. This,in turn, reduces the effective sensitivity of each image capture system.In certain applications, the reduction of effective sensitivity may notbe preferred.

Thus, there remains a need for image capture systems capable ofsimultaneous image capture using more than one image capture systemwithout a substantial reduction in the effective sensitivity of eachsystem.

Further there is a need for image capture systems having a reduceddependence upon post capture processing of the electronic image. Suchpost image capture processing is typically performed because theelectronic image is often presented on a display screen that hassubstantially lower image display resolution than the image captureresolution of the imager used to capture the electronic image. Thus theelectronic image must typically be downsampled so that it can bepresented on the lower resolution display. Such processing can be timeconsuming which can delay the presentation of the evaluation imageand/or the capture of additional images.

More particularly, there is a need for image capture systems and methodsthat permit simultaneous capture of images using an imaging system thatcaptures archival images on a photosensitive element and an imagingsystem that captures images using a solid state imaging surface andgenerates evaluation images therefrom.

SUMMARY OF THE INVENTION

In one aspect, an imaging system is provided. The imaging system has ataking lens unit adapted to focus light from a scene, and a beamsplitter receiving light from the scene with a portion of the receivedlight traveling from the beam splitter to a first imaging surface and aportion of the received light traveling from the beam splitter to asecond imaging surface. A first image capture system is provided forcapturing an image based upon the light traveling to the first imagingsurface, and a second image capture system is provided for capturing asecond image based upon the image formed at the second imaging surface.An array of micro-lenses is in optical association with the firstimaging surface, with each micro-lens in the array concentrating a firstfraction of the light from the beam splitter onto concentrated imageareas of the first imaging surface. Wherein the first image capturesystem forms an image based upon the light concentrated onto theconcentrated image areas.

In another aspect, an image capture system is provided. The imagingsystem has a taking lens unit adapted to focus light toward a beamsplitter and a beam splitter receiving light from the taking lens unitand passing a portion of light to form an image at a first imagingsurface and a portion of the light to form an image at a second imagingsurface. A photosensitive element image capture system having a shutterassembly controls the passage of light to at least one imaging surfaceand a photosensitive element positioning system having a gatepositioning a photosensitive element having the first imaging surfacethereon to receive light controlled by the shutter assembly. Anelectronic image capture system is provided having an image sensor withthe second imaging surface thereon said electronic image capture systemis adapted to capture an image based upon the light incident on thesecond image surface and a micro-lens array in optical association withthe second imaging surface imaging plane concentrating light directed atconcentrated image areas of the second imaging surface. A controllerdetermines a capture time and enables the shutter assembly andelectronic image capture system to capture an image representative ofscene conditions during the capture time.

In another aspect, an imaging system is provided. The imaging systemshas a taking lens unit adapted to focus light from a scene and an imagecapture system for capturing an image based upon the light traveling toan imaging surface. A stacked array magnifier is positioned to alter theeffective magnification of the light traveling to the imaging surface.An array of micro-lenses in optical association with the imagingsurface, with each micro-lens in the array concentrating a firstfraction of the light onto concentrated image areas of the imagingsurface. Wherein the image capture system forms an image based upon thelight concentrated onto the concentrated image areas.

In still another aspect, a method for capturing an image of a sceneusing a first imaging surface having a first sensitivity and a secondimaging surface having a second sensitivity is provided. In accordancewith the method, light from the scene is focused and the focused lightfrom the scene is divided into a first portion traveling to a firstimaging surface and a second portion traveling to a second imagingsurface. A fraction of the light traveling along the first axis isconcentrated to form a pattern of concentrated image elements on thefirst imaging surface. A first image is formed based upon the pattern ofconcentrated image elements formed on the first imaging surface. Asecond image is formed based upon the light reaching the second imagingsurface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of an embodiment of an imaging system of thepresent invention;

FIG. 2 schematically illustrates a face view of an image sensor;

FIG. 3 is an illustration of a back view of the imaging system of FIG.1;

FIG. 4 is an illustration of one embodiment of a face view of an imagesensor with an optically associated array of micro-lenses;

FIG. 5 is a side illustration of one embodiment of an image sensor andarray of micro-lenses shown in FIG. 4;

FIG. 6A is a diagram useful in describing the relationship between sceneexposure, actual latitude and effective latitude;

FIG. 6B is a diagram useful in describing the effect of concentratedlight on a photosensitive element;

FIG. 6C is a diagram useful in describing the effect of residual lighton the photosensitive element;

FIG. 7A schematically illustrates a face view of another embodiment ofan image sensor with an optically associated array of micro-lenses ofthe invention;

FIG. 7B schematically illustrates a side view of the embodiment of FIG.7A;

FIGS. 8A-8E show various diagrams illustrating embodiments of an arrayof micro-lenses useful in practicing the present invention;

FIGS. 9A-9C show diagrams illustrating various embodiments of arrays ofdifferent micro-lenses that can be usefully combined in a single arrayof micro-lenses;

FIGS. 9D-9F show diagrams illustrating patterns formed on an imagesensor by imagewise exposure of the image sensor to light from a scenepassing through, respectively, the arrays of FIGS. 9A-9C;

FIGS. 10A-10C show cross-section illustrations of arrays ofmicro-lenses, spherical and aspherical lenses;

FIG. 11 shows a flow chart of imaging according to the invention;

FIG. 12 shows a contrast pattern formed on an image sensor afterimagewise exposure of the image sensor;

FIG. 13 is an illustration of another embodiment of an imaging system ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a block diagram of one embodiment of an imaging system 4.As is shown in FIG. 1, imaging system 4 includes a taking lens unit 6,which focuses light from a scene (not shown) along a first axis A.Imaging system 4 further includes a beam splitter 8. Beam splitter 8receives light traveling along first axis A and passes a portion of thereceived light so that it continues to travel along first axis A. Beamsplitter 8 also directs another portion of the received light along asecond axis B.

Beam splitter 8 can be any conventional beam splitter as known in theoptical arts. In certain embodiments, beam splitter 8 can comprise anangled glass surface, partially silvered mirrors, a beam splitting prismand/or a combination thereof. Beam splitter 8 can operate by passing afirst portion of the received light through beam splitter 8 so that thefirst portion continues to travel along first axis A while alsodirecting a second portion of the received light in a second directionas described above. Alternatively, beam splitter 8 can direct a portionof the received light traveling along first axis A so that one portionof the light travels along second axis B and another portion of thelight from taking lens unit 6 along a third axis (not shown), with thefirst, second and third axes being different.

Imaging system 4 has more than one image capture system with a firstimage capture system 10 being provided having a first imaging surface 11for capturing an image based upon light that travels along first axis Aand a second image capture system 20 being provided having a secondimaging surface 21 for capturing an image of the scene based upon lightthat travels along second axis B. In the embodiment shown, first imagingsurface 11 comprises a surface on a conventional photosensitive element14 such as a film or a plate. Also in the embodiment of FIG. 1, secondimaging surface 21 comprises a surface on an electronic image sensor 24that is positioned to receive light directed by beam splitter 8 alongsecond axis B. The operation of the first image capture system 10 andthe second image capture system 20 will be discussed in detail below.

Because beam splitter 8 divides the light from taking lens unit 6between first imaging surface 11 and second imaging surface 21, theamount of light that reaches each imaging surface per unit of time isreduced and consequently, the effective system sensitivities of thefirst image capture system 10 and the second image capture system 20 arereduced. However, as is shown, in FIG. 1, a micro-lens array 12 isoptically associated with one of the imaging surfaces and enhances theexposure at selected portions of the associated imaging surfaces. Thiseffectively increases the sensitivity of the selected portions andeffectively decreases the sensitivity of other portions. This increasedsensitivity can be used to compensate for the loss of the light that isdisplaced by beam splitter 8 so that an image formed using imaginginformation from the selected portions will have the appearance of animage captured with a system having greater sensitivity. In certainembodiments described below, imaging information is obtained from bothregions having increased and decreased sensitivity and this imaginginformation is combined to form an image having an effectively increasedoverall dynamic range.

It will be appreciated that beam splitter 8 can be adapted to direct aprincipal portion of the light from a scene toward first imaging surface11 while directing the remaining portion of the light from the scenetoward second imaging surface 21 that is optically associated with amicro-lens array 12 to compensate for the reduced provision of light atsecond imaging surface 21. This allows first image capture system 10 touse conventional image capture techniques to form an image using thelight that strikes the first imaging surface. In this regard, the degreeof concentration provided by the micro-lenses can be defined so that theeffective sensitivity or effective dynamic range of the second imagecapture system 20 to the concentrated light will approximate theresponse of the first imaging surface to the light from beam splitter 8.

For example, in one potential embodiment of the imaging system 4 shownin FIG. 1, beam splitter 8 passes between 75 percent and 95 percent ofthe light from taking lens unit 6 to first imaging surface 11 anddirects the remaining portions of light from taking lens unit 6 tosecond imaging surface 21. In this example, array of micro-lenses 12 ispositioned in optical association with second imaging surface 21 andadapted to concentrate light received in the second optical path B sothat second image capture system 20 can derive an image from lightconcentrated by micro-lens array 12 to form an image having an apparentsensitivity that approximates the sensitivity of the first image capturesystem 10. Beam splitter 8 can direct proportions of light betweenalternate paths in other ratios. The distribution of light by beamsplitter 8 can be at any distribution ratio consistent with the intendeduse. For image capture systems that have grossly similar nativesensitivities, the distribution is generally at a ratio of between 19:1and 1:19, preferably at a ratio of between 3:1 and 1:3, and morepreferable at a ratio of between 2:1 and 1:2. More disparate ratios canbe employed with image capture systems that have grossly differentnative sensitivities.

First Image Capture System

In the embodiment shown in FIG. 1 first image capture system 10comprises a photosensitive element positioning system 13 and ashuttering system 23. Photosensitive element positioning system 13 has agate system 15 that positions photosensitive element 14 to receive animage formed by light from the scene traveling along first axis A. Wherephotosensitive element 14 is adapted to record multiple images onseparate image areas of photosensitive element 14 such as wherephotosensitive element 14 comprises a roll of a flexible film capable ofreceiving images in multiple frame areas, photosensitive elementpositioning system 13 can also comprise a film supply system 16 and afilm take up system 17 that cooperate to advance photosensitive element14 between frame areas. Film supply system 16 and film take up system 17can comprise many well known conventional structures and mechanisms foradvancing and positioning a photosensitive element 14.

In the embodiment shown in FIG. 1, photosensitive element positioningsystem 13 is also shown including an optional contact surface 18 whichis used to help establish the positioning, flatness and alignment ofphotosensitive element 14. Where contact surface 18 is provided,photosensitive element 14 is brought against photosensitive elementcontact surface 18 prior to image capture. Contact surface 18 provides arigid flat structure that is positioned at an appropriate location toreceive the image. Photosensitive element contact surface 18 is adaptedto contact photosensitive element 14 without damaging photosensitiveelement 14 and to hold photosensitive element 14 in a manner thatimproves the positioning flatness and alignment of photosensitiveelement 14. Photosensitive element contact surface 18 can, for example,have matte beads (not shown) distributed thereon as are known in the artof photography. Such matte beads can have a diameter of between 0.1 to 2micro-meters and a distribution generally covering the surface area ofphotosensitive element contact surface 18. Coatings of various materialscan also be used, such as, for example, mineral oil, silicone oil andcarnuba wax. Other materials that can usefully be used withphotosensitive element contact surface 18 are described in a paperentitle “Coating Physical Property Modifying Addenda” IX published inResearch Disclosure 38957, Volume 389 in September 1996. It isrecognized that insertion of optional element contact surface 18introduces additional refractive surfaces which can be accommodated asis well understood in the optical arts.

As is also shown in FIG. 1, an optional pressure plate assembly 19 isused to position photosensitive element 14 against element contactsurface 18. Optional pressure plate assembly 19 can be formed by guidesor rails integral to a film positioning system 13, or gate system 15.Photosensitive element contact surface 18 and optional pressure plateassembly 19 can be individually or collectively reversibly compressibleand act to passively position photosensitive element 14 in a position toreceive light from the scene.

Shutter system 23 is disposed between the light from the scene andphotosensitive element 14. Shutter system 23 is adapted to control thepassage of light from the scene to first imaging surface 11. Shuttersystem 23 passes light from the scene in response to signals generatedby user controls 58 or microprocessor 50. These signals cause shuttersystem 23 to move from a closed state that prevents light from passingto an open state that permits light to pass for a first capture period.At the end of the first capture period, shutter system 23 returns to theclosed state. The duration of the first capture period can be fixed orit can be determined, for example, by microprocessor 50 usingconventional algorithms that are based upon the amount of light from thescene as determined by using photosensors well known in the art, andinformation indicating the photosentivity of the photosensitive element14. The amount of light in the scene can be determined using aphotosensor (not shown) and using conventional exposure determiningalgorithms. Alternatively, image sensor 24 can be used to determine theamount of light in the scene. Similarly, the photosensitivity ofphotosensitive element 14 can be determined, for example, by analysis ofmarkings on a film canister, or by using other means well known in theart.

The operation of taking lens unit 6 will now be described in greaterdetail. Taking lens unit 6 focuses light from the scene so that lightpassing through beam splitter 8 forms an image of the scene at firstimaging surface 11 and second imaging surface 21. Optionally additionaloptical elements (not shown) can be interposed between beam splitter 8and first imaging surface 11 and/or second imaging surface 21 to helpfocus light so that corresponding images are formed at first imagingsurface 11 and/or second imaging surface 21.

Taking lens unit 6 can be simple, such as having a single focal lengthwith manual focusing or a fixed focus. In the example embodiment shownin FIG. 1, taking lens unit 6 is a motorized 2× zoom lens unit in whicha mobile element or combination of elements 26 are driven, relative to astationary element or combination of elements 28 by a lens driver 30. Inthe embodiment shown, lens driver 30 controls both the lens focal lengthand the lens focus position. A viewfinder system 32 presents imagescaptured by image sensor 24 to user 5 to help user 5 to compose images.The operation of viewfinder system 32 will be described in detail below.

Various methods can be used to determine the focus settings of takinglens unit 6. In a preferred embodiment, image sensor 24 is used toprovide multi-spot autofocus using what is called the “through focus” or“whole way scanning” approach. The scene is divided into a grid ofregions or spots, and the optimum focus distance is determined for eachimage region. The optimum focus distance for each region is determinedby moving taking lens system 6 through a range of focus distancepositions, from the near focus distance to the infinity position, whilecapturing images. Depending on the camera design, between four andthirty-two images may need to be captured at different focus distances.Typically, capturing images at eight different distances providessuitable accuracy.

The captured image data is then analyzed to determine the optimum focusdistance for each image region. This analysis begins by band-passfiltering the sensor signal using one or more filters, as described incommonly assigned U.S. Pat. No. 5,874,994 “Filter Employing ArithmeticOperations for an Electronic Synchronized Digital Camera” filed by Xieet al., on Dec. 11, 1995, the disclosure of which is herein incorporatedby reference. The absolute value of the bandpass filter output for eachimage region is then peak detected, in order to determine a focus valuefor that image region, at that focus distance. After the focus valuesfor each image region are determined for each captured focus distanceposition, the optimum focus distances for each image region can bedetermined by selecting the captured focus distance that provides themaximum focus value, or by estimating an intermediate distance value,between the two measured captured focus distances which provided the twolargest focus values, using various interpolation techniques.

The lens focus distance to be used to capture the final high-resolutionstill image can now be determined. In a preferred embodiment, the imageregions corresponding to a target object (e.g. a person beingphotographed) are determined. The focus position is then set to providethe best focus for these image regions. For example, an image of a scenecan be divided into a plurality of subdivisions. A focus evaluationvalue representative of the high frequency component contained in eachsubdivision of the image can be determined and the focus evaluationvalues can be used to determine object distances as described incommonly assigned U.S. Pat. No. 5,877,809 entitled “Method Of AutomaticObject Detection In An Image”, filed by Omata et al. on Oct. 15, 1996,the disclosure of which is herein incorporated by reference. If thetarget object is moving, object tracking may be performed, as describedin commonly assigned U.S. Pat. No. 6,067,114 entitled “DetectingCompositional Change in Image” filed by Omata et al. on Oct. 26, 1996,the disclosure of which is herein incorporated by reference. In analternative embodiment, the focus values determined by “whole wayscanning” are used to set a rough focus position, which is refined usinga fine focus mode, as described in commonly assigned U.S. Pat. No.5,715,483, entitled “Automatic Focusing Apparatus and Method”, filed byOmata et al. on Oct. 11, 1998, the disclosure of which is hereinincorporated by reference.

In one embodiment, the bandpass filtering and other calculations used toprovide autofocus in imaging system 4 are performed by digital signalprocessor 40. In this embodiment, imaging system 4 uses a speciallyadapted image sensor 24, as is shown in commonly assigned U.S. Pat. No5,668,597 entitled “Electronic Camera With Rapid Autofocus Upon AnInterline Image Sensor”, filed by Paruiski et al. on Dec. 30, 1994, thedisclosure of which is herein incorporated by reference, toautomatically set the lens focus position. As described in the '597patent, only some of the lines of sensor photoelements (e.g. only ¼ ofthe lines) are used to determine the focus. The other lines areeliminated during the sensor readout process. This reduces the sensorreadout time, thus shortening the time required to focus taking lensunit 6.

In an alternative embodiment, imaging system 4 uses a separate opticalor other type (e.g. ultrasonic) of rangefinder 48 to identify thesubject of the image and to select a focus position for taking lens unit6 that is appropriate for the distance to the subject. Rangefinder 48operates lens driver 30, directly or as shown in FIG. 1 microprocessor50 uses information from rangefinder 48, to move one or more mobileelements 26 of taking lens unit 6. Rangefinder 48 can be passive oractive or a combination of the two. A wide variety of multiple sensorrangefinders 48 known to those of skill in the art are suitable for use.For example, U.S. Pat. No. 5,440,369 entitled “Compact Camera WithAutomatic Focal Length Dependent Exposure Adjustments” filed by Tabataet al. on Nov. 30, 1993, the disclosure of which is herein incorporatedby reference, discloses such a rangefinder 48. Rangefinder 48 canoperate lens driver 30 directly or as is shown in the embodiment of FIG.1, rangefinder 48 can provide data to microprocessor 50. In the latterembodiment, microprocessor 50 uses this data to determine how to moveone or more mobile elements 26 of taking lens unit 6 to set the focallength and lens focus position of taking lens unit 6.

The focus determination made by rangefinder 48 can be of the single-spotor multi-spot type. Preferably, the focus determination uses multiplespots. In multi-spot focus determination, the scene is divided into agrid of regions or spots, and the optimum focus distance is determinedfor each spot.

Once the optimum distance to the subject is determined, microprocessor50 causes lens driver 30 to adjust the at least one element 26 to setthe focal length and lens focus position of taking lens unit 6. In theembodiment of FIG. 1, a feedback loop is established between lens driver30 and microprocessor 50 so that microprocessor 50 can accurately setthe focal length and the lens focus position of taking lens unit 6.

Second Image Capture System

FIG. 2 shows a face view of image sensor 24. As can be seen in FIG. 2image sensor 24 has a discrete number of photosensors 25 arranged in atwo-dimensional array. Image sensor 24 can take many forms, for exampleimage sensor 24 can be a conventional charge coupled device (CCD)sensor, a complementary metal oxide semiconductor (CMOS) image sensorand/or a charge injection device (CID). In one example embodiment, imagesensor 24 has an array of 2448×1632 photosensitive elements orphotosensors 25. Photosensors 25 of image sensor 24 convert photons oflight from the scene into electron charge packets. Each photosensor 25is surrounded with inactive areas 27 such as isolation regions,interconnecting circuitry and useful structures known to those ofordinary skill in the art. Each photosensor 25 on image sensor 24corresponds to one pixel of an image captured by image sensor 24,referred to herein as an initial image.

In one embodiment, where image sensor 24 is used to capture colorimages, each photosensor 25 is also overlaid with a color filter array,such as the Bayer color filter array described in commonly assigned U.S.Pat. No. 3,971,065, entitled “Color Imaging Array” filed by Bayer onMar. 7, 1975, the disclosure of which is herein incorporated byreference. The Bayer color filter array has 50% green pixels in acheckerboard mosaic, with the remaining pixels alternating between redand blue rows. Each photosensor 25 responds to the appropriately coloredincident light illumination to provide an analog signal corresponding tothe intensity of illumination incident on the photosensor 25. Variousother color filter arrays can be used. A color filter can be omittedwhere image sensor 24 is used to capture grey scale or so-called blackand white images. In another embodiment, color images can be captured bywavelength specific color exposure depth interrogation as described inU.S. Pat. No. 5,965,875 entitled “Color Separation in an Active PixelCell Imaging Array Using a Triple Well Structure,” filed by Merrill onApr. 24, 1998.

The process by which second image capture system 20 converts informationfrom image sensor 24 into a digital image will now be described withreference to FIG. 1. The analog output of each photosensor 25 isamplified by an analog amplifier (not shown) and analog processed by ananalog signal processor 34 to reduce the output amplifier noise of imagesensor 24. The output of the analog signal processor 34 is converted toa captured digital image signal by an analog-to-digital (A/D) converter36, such as, for example, a 10-bit AID converter that provides a 10 bitsignal in the sequence of the Bayer color filter array.

The digitized image signal is temporarily stored in a frame memory 38,and is then processed using a programmable digital signal processor 40as described in commonly assigned U.S. Pat. No. 5,016,107 entitled“Electronic Still Camera Utilizing Image Compression and DigitalStorage” filed by Sasson et al. on May 9, 1989, the disclosure of whichis herein incorporated by reference. The image processing includes aninterpolation algorithm to reconstruct a full resolution color initialimage from the color filter array pixel values using, for example, themethods described in commonly assigned U.S. Pat. No. 5,373,322 entitled“Apparatus and Method for Adaptively Interpolating a Full Color ImageUtilizing Chrominance Gradients” filed by LaRoche et al. on Jun. 30,1993, and U.S. Pat. No. 4,642,678 entitled “Signal Processing Method andApparatus for Producing Interpolated Chrominance Values in a SampledColor Image Signal” filed by Cok on Feb. 3, 1986, the disclosures ofwhich are herein incorporated by reference. White balance, whichcorrects for the scene illuminant, is performed by multiplying the redand blue signals by a correction factor so that they equal green forneutral (i.e. white or gray) objects. Preferably, color correction usesa 3×3 matrix to correct the camera spectral sensitivities. However,other color correction schemes can be used. Tone correction uses a setof look-up tables to provide the opto-electronic transfer characteristicdefined in the International Telecommunication Union standard ITU-RBT.709. Image sharpening, achieved by spatial filters, compensates forlens blur and provides a subjectively sharper image. Luminance andchrominance signals are formed from the processed red, green, and bluesignals using the equations defined in ITU-R BT.709.

Digital signal processor 40 uses the initial images to create archivalimages of the scene. Archival images are typically high resolutionimages suitable for storage, reproduction, and sharing. Archival imagesare optionally compressed using the JPEG standard and stored in datamemory 44. The JPEG compression standard uses the well-known discretecosine transform to transform 8×8 blocks of luminance and chrominancesignals into the spatial frequency domain. These discrete cosinetransform coefficients are then quantized and entropy coded to produceJPEG compressed image data. This JPEG compressed image data is storedusing the so-called “Exif” image format defined in “The ExchangeableImage File Format (Exif)” version 2.1, published by the JapanElectronics and IT Industries Association JEITA CP-3451. The Exif formatarchival image can also be stored in memory card 52. In the embodimentof FIG. 1, imaging system 4 is shown having a memory card slot 54 whichholds removable memory card 52 and has a memory card interface 56 forcommunicating with memory card 52. An Exif format archival image and anyother digital data can also be transmitted to a host computer or otherdevice (not shown), which is connected to imaging system 4 through acommunication module 46.

Communication module 46 can take many known forms. For example, anyknown optical, radio frequency or other transducer can be used. Suchtransducers convert image and other data into a form such as an opticalsignal, radio frequency signal, or other form of signal that can beconveyed by way of a wireless, wired, or optical network such as acellular network, satellite network, cable network, telecommunicationnetwork, the internet or any other communication path to a host computer(not shown), network (not shown) or other device including but notlimited to a printer, internet appliance, personal digital assistant,telephone or television.

Digital signal processor 40 also creates smaller size digital imagesbased upon the initial images. These smaller sized images are referredto herein as evaluation images. Typically, the evaluation images arelower resolution images adapted for display on viewfinder display 33 orexterior display 42. Viewfinder display 33 and exterior display 42 cancomprise, for example, a color liquid crystal display (LCD), organiclight emitting display (OLED) also known as an organicelectroluminescent display (OELD) or a subset of the OLED type displaythat uses polymeric compounds to emit light (also known as a PLED). Anyother type of video display can also be used.

Image Capture Sequence

The process by which images are captured will now be described. Thesteps of this process are referred to herein collectively as an “imagecapture sequence”. As used herein, the term “image capture sequence”comprises at least an image capture phase and can optionally alsoinclude a composition phase and a verification phase.

During the composition phase, microprocessor 50 sends signals to atiming generator 66 indicating that images are to be captured. Timinggenerator 66 is connected generally to the elements of second imagecapture system 20, as shown in FIG. 1, for controlling the digitalconversion, compression, and storage of the image signal. Image sensor24 is driven from timing generator 66 via sensor driver 68.Microprocessor 50, timing generator 66 and sensor driver 68 cooperate tocause image sensor 24 to collect charge in the form of light from ascene for an integration time also referred to herein as a secondcapture time that is either fixed or variable. After the second capturetime is complete an image signal is provided to analog signal processor34 and converted into evaluation images as is generally described above.

A stream of initial images is captured in this way and digital signalprocessor 40 generates a stream of evaluation images based upon theinitial images. The stream of evaluation images is presented onviewfinder display 33 or exterior display 42. User 5 observes the streamof evaluation images and uses the evaluation images to compose theimage. The evaluation images can be created as described above using,for example, resampling techniques such as are described in commonlyassigned U.S. Pat. 5,164,831 entitled “Electronic Still Camera ProvidingMulti-Format Storage Of Full And Reduced Resolution Images” filed byKuchta et al., on Mar. 15, 1990, the disclosure of which is hereinincorporated by reference. The evaluation images can also be stored, forexample, in data memory 44.

During the capture phase, microprocessor 50 sends a capture signalcausing digital signal processor 40 to obtain an initial image and toprocess the initial image to form an evaluation image. During thecapture phase, microprocessor 50 also sends a signal causing shuttersystem 23 to expose photosensitive element 14 to light from the scenefor a capture time during which the photosensitive element 14 collectslight from the scene to form an image. Microprocessor 50 also sends acapture signal to second image capture system 20 causing digital signalprocessor 40 to select an initial image as an evaluation image and,optionally, to process the initial image to form an additional archivalimage.

First image capture system 10 and second image capture system 20, formimages based upon light that is received during the first capture timeand a second capture time respectively. Depending on the sensitivitiesof the imaging surfaces used to collect light, the capture time used byone imaging system to capture an image can be different from the capturetime used by the other imaging system to capture an image.Microprocessor 50 determines an appropriate capture time for each imagecapture system based upon scene conditions, knowledge of the sensitivityof the first imaging surface 11 and the second imaging surface 21, andbased upon the type of photography being performed, causes appropriatesignals to be generated for the capture of images by each image capturesystem. Various conventional algorithms can be used to define the firstcapture time and second capture time for either or both of the imagecapture systems.

During the verification phase, the evaluation image is adapted forpresentation on viewfinder display 33 and/or exterior display 42 and ispresented for a period of time. This permits user 5 to verify that theappearance of the captured archival image is acceptable. Because boththe archival image and the evaluation image are derived from a singleoptical system, i.e. taking lens unit 6, these images contain the sameimage information and it is not necessary to correct for parallaxproblems created in evaluation images when one optical system is used toprovide an archival image of a scene to a first image capture system 10and a second, separate, optical system is used to provide a second imagecapture system 20 used to capture evaluation images.

Imaging system 4 is controlled by user controls 58, some of which areshown in more detail in FIG. 3. User controls 58 can comprise any formof transducer or other device capable of receiving input from user 5 andconverting this input into a form that can be used by microprocessor 50in operating imaging system 4. For example, user controls 58 cancomprise touch screen input a 4-way switch, a 6-way switch, an 8-wayswitch, stylus system, track ball system, joy stick system, a voicerecognition system, a gesture recognition system and other such systems.In the embodiment shown in FIG. 2, user controls 58 include a shuttertrigger button 60. User 5 initiates image capture by depressing shuttertrigger button 60. This causes a trigger signal to be transmitted tomicroprocessor 50. Microprocessor 50 receives the trigger signal andgenerates capture signals in response to the trigger signal that causean image to be captured by one or both of the first image capture system10 and the second image capture system 20.

In the embodiment shown in FIG. 3, user controls 58 also include a“wide” zoom lens button 62 and a “tele” zoom lens button 64, areprovided which together control both a 2:1 optical zoom and a 2:1digital zoom feature. The optical zoom is provided by taking lens unit6, and adjusts the magnification in order to change the field of view ofthe focal plane image captured by image sensor 24. The digital zoom isprovided by the digital signal processor 40, which crops and resamplesthe captured image stored in frame memory 38. When user 5 first turns onimaging system 4, the zoom lens is set to the 1:1 position, so that allsensor photoelements are used to provide the captured image, and thetaking lens unit 6 is set to the wide angle position. In a preferredembodiment, this wide angle position is equivalent to a 40 mm lens on a35 mm film camera. This corresponds to the maximum wide angle position.

When user 5 then depresses the “tele” zoom lens button 64, taking lensunit 6 is adjusted by microprocessor 50 via lens driver 30 to movetaking lens unit 6 towards a more telephoto focal length. If user 5continues to depress the “tele” zoom lens button 64, the taking lensunit 6 will move to the full optical 2:1 zoom position. In a preferredembodiment, this full telephoto position is equivalent to a 40 mm lenson a 35 mm film camera. If user 5 continues to depress the “tele” zoomlens button 64, the taking lens unit 6 will remain in the full optical2:1 zoom position, and digital signal processor 40 will begin to providedigital zoom, by cropping (arid optionally resampling) a central area ofthe image. While this increases the apparent magnification of the secondimage capture system 20, it causes a decrease in sharpness, since someof the outer photoelements of the sensor are discarded when producingthe archival image. However, this decrease in sharpness would normallynot be visible on the relatively small viewfinder display 33 andexterior display 42.

For example, in the embodiment shown in FIG. 1, second image capturesystem 20 derives an evaluation image from a high resolution imagesensor 24 having, for example, 2448×1632 photosensors corresponding toabout 4.0 megapixels. The term resolution is used herein to indicate thenumber of picture elements used to represent the image. Exterior display42, however, has lower resolution providing, for example, 320×240elements, which correspond to about 0.08 megapixels. Thus, there arcabout 50 times more sensor elements than display elements. Accordingly,it is necessary to resample the initial image into an evaluation imagehaving a suitably small image size so that it can properly fit onviewfinder display 33 or exterior display 42. This resampling can bedone by using low pass filtering, followed by sub-sampling, or by usingbilinear interpolation techniques with appropriate anti-aliasingconditioning. Other techniques known in the art for adapting a highresolution image for display on a relatively low resolution display canalternatively be used.

The resampling of the captured image to produce an evaluation imagehaving fewer pixels (i.e. lower resolution) than the captured image isperformed by digital signal processor 40. As noted earlier, digitalsignal processor 40 can also provide digital zooming. In the maximum 2:1setting, digital signal processor 40 uses a central area such as an areacomprising 640×480 photosites to form an image and interpolates theimaging information from these photosites to obtain an image having, forexample, 1280×960 or 2448×1632 samples to provide the image.

Digital signal processor 40 can also modify the evaluation images inother ways so that the evaluation images match the appearance of acorresponding archival image when viewed on viewfinder display 33 orexterior display 42. These modifications include color calibrating theevaluation images so that when the evaluation images arc presented onviewfinder display 33 or exterior display 42, the displayed colors ofthe evaluation image appear to match the colors in the correspondingarchival image. These and other modifications help to provide user 5with an accurate representation of the color, format, scene content andlighting conditions that will be present in a corresponding archivalimage.

As noted above, because evaluation images are displayed using anelectronic display that has lower resolution than a correspondingarchival image, an evaluation image may appear to be sharper when viewedthrough viewfinder display 33 or exterior display 42 than it will appearwhen the archival image is printed or otherwise displayed at higherresolution. Thus, in one optional embodiment of the present invention,each evaluation image can be modified so that areas that will appear outof focus in a corresponding archival image could appear to be out offocus when viewed on an electronic display such as exterior display 42.Moreover, when the digital zoom is active, the entire image is softened,but this softening would normally not be visible in exterior display 42.For the example in imaging system 4 of FIG. 1, exterior display 42 canbe a display having 320×240 pixels while the archival image is providedusing a sensor area of 640×480 pixels in the maximum digital zoomsetting. Thus, the evaluation image displayed on exterior display 42after normal resizing will appear suitably sharp. However, the archivalimage will not produce an acceptably sharp print. Therefore, aresampling technique can be used which creates an evaluation imagehaving 320×240 pixels, but having reduced apparent sharpness when themaximum digital zoom setting is used, as is described in commonlyassigned U.S. patent application Ser. No. 10/028,644 entitled “Methodand Imaging system for Blurring Portions of a Verification Image To ShowOut of Focus Areas in a Captured Archival Image”, filed by Belz, et al.on Dec. 21, 2001.

It will be appreciated that the apparent sharpness of a print or othertangible output that is made from the archival image is also a functionof the size of the rendered image. Accordingly, imaging system 4 canoptionally have an input (not shown) for receiving a signal indicatingthe expected size of the output and can adjust the apparent sharpness ofthe evaluation image accordingly and/or provide a warning as is alsodescribed in the '644 application.

Micro-lens Array

As is noted above, the amount of light that is available to each offirst image capture system 10 and second image capture system 20 duringa capture time is effectively reduced because the light passing from thescene through taking lens unit 6 is shared between first image capturesystem 10 and second image capture system 20. This effectively reducesthe effective sensitivity of first image capture system 10 and secondimage capture system 20. In accordance with the present invention, theeffective sensitivity of at least one of first image capture system 10and second image capture system 20 is enhanced by optically associatinga micro-lens array 12 with at least one of the first image capturesystem 10 and the second image capture system 20. In the embodiment ofFIG. 1, micro-lens array 12 is positioned between beam splitter 8 andsecond imaging surface 21. The function of micro-lens array 12 will nowbe described with reference to FIGS. 4 and 5.

FIG. 4 schematically illustrates a face view of one embodiment ofmicro-lens array 12 and an associated image sensor 24 according to theinvention. As is shown in FIG. 4, image sensor 24 has a second imagingsurface 21 with photosensors 25, and light non-responsive inactive areas27, such as isolation regimes, drains and interconnectivity regions. Theprojection of individual dynamic range enhancement micro-lenses 72 ofmicro-lens array 12 is shown relative to photosensors 25.

FIG. 5 schematically illustrates a cross section view of the embodimentof FIG. 4. As is shown in FIG. 5, light from a scene striking eachdynamic range enhancement micro-lens 72 is focused at an associatedconcentrated image area 74 of image sensor 24. At least one photosensorin a concentrated image area 25 b is positioned within each concentratedimage area 74 associated with each dynamic range enhancement micro-lens72. Photosensors in a concentrated image area 25 b within eachconcentrated image area 74 receive enhanced exposure thereby increasingthe effective sensitivity of photosensors in a concentrated image area25 b within concentrated image area 74. This makes it possible to imagedark scene elements such as scene shadows. Photosensors in a residualimage area 25 a that are outside of concentrated image area 74 arelocated in residual image area 76. Photosensors in a residual image area25 a receive a reduced exposure. This is because a portion of the lightthat would have traveled to photosensors 25 a in residual image areas 76is focused by each dynamic range enhancement micro-lens 72 ontoconcentrated image areas 74. This effectively filters the amount oflight passing to photosensors 25 a in residual image areas 76 reducingthe effective sensitivity of photosensors 25 a. Thus, each dynamic rangeenhancement micro-lens 72 concentrates light at concentrated image area74 and enhances the exposure at photosensitive area 25 b while retardingthe exposure of residual image area 76 and reducing exposure atphotosensitive area 25 a.

The operation of this system can be explained with reference to FIGS.6A, 6B and 6C. As is shown in FIG. 6A, light from a photographic sceneextends over a wide range of scene luminances. In the case of consumerphotography, these are typically the luminances that are visuallyobservable by humans. This range is indicated in FIG. 6A as sceneluminance range 80. However, photosensors 25 on image sensor 24 has anactual latitude 82 within which photosensors 25 can capture differencesin scene illumination and record a contrast image of the scene. Becauseof the inherent limitations of solid-state image capture technology andthe specific response of photosensors 25 to illumination from the scene,the actual photosensor latitude 82 of photosensors 25 is defined by alower response threshold 84 and an upper response threshold 86.Photosensor 25 does not differentiably react to scene illuminationdifferences when photosensor 25 is exposed to quantities of light thatare lower than the lower response threshold 84. This is in part becausethe amount of charge stored at the photosensor 25 during an imagecapture sequence can be so low as to be indistinguishable from errantelectrical interference or other noise that can become involved withsignals transmitted from the imager. This effect practically occurs whenthe signal to noise ratio of the exposure matches the inherent darksignal to noise ratio of image sensor 24.

Similarly, photosensor 25 does not differentiably react to sceneillumination differences when element 30 is exposed to quantities oflight that are higher than the upper response threshold 86. As noted ingreater detail above, this is because the amount of light received byphotosensor 25 above upper response threshold 86 is sufficient fill thecharge storage capacity of photosensor 25 of image sensor 24 so thatphotosensor 25 no longer has a meaningful additional response toadditional light energy. Because of this, all photosensors 25 that areexposed to such quantities of light cease to record meaningfuldifferences in scene content.

However, as is also shown in FIG. 6A, it is desirable that second imagecapture system 20 and image sensor 24 should record scene information ata desired system latitude 88 having desired system lower responsethreshold 90 that is lower than the lower response threshold 84 ofphotosensors 25 of image sensor 24. Photography in this range ofillumination is made possible by concentrating light from the scene. Inthis regard, each of micro-lenses 72 in micro-lens array 12 fractureslight from the scene into at least two portions. A concentrated fractionof light from the scene is concentrated so that a greater amount oflight per unit area falls upon each of photosensors 25 b within theconcentrated image areas 74 during a capture time than would fall uponphotosensors 25 b within concentrated image areas 74 in the absence ofthe array of micro-lenses 12 of dynamic range enhancement micro-lenses72.

As is shown in FIG. 6B, this increase in the amount of light incidentupon photosensors 25 b within concentrated image areas 74 has the effectof shifting a first range of scene exposure levels 94 so that the entirefirst range 94 is within actual photosensor latitude 82 allowingphotosensors 25 b within concentrated image 74 record an image.

As is shown in FIG. 6C, some of the light incident on micro-lenses 72,for example light that is poorly focused by micro-lenses 72 or lightthat passes between distinct ones of micro-lenses 72, is notconcentrated. Instead, this residual fraction of the light passes toimage sensor 24 and is incident on photosensors 25 a of residual imagearea 76 thus enabling formation of a residual image. The residual imagecan further be formed by designed or adventitious light scatter andreflection at image sensor 24 The residual fraction of light thatstrikes residual image area 76 during a second capture time is less thanthe amount of light that would be incident on residual image area 76 inthe event that array 12 of micro-lenses 72 was not interposed between ascene and image sensor 24 during the same second capture time. Thus,micro-lenses 72 effectively filter light from the scene that is incidenton residual image area 76 so that a greater quantity of light must beavailable during the second capture time in order for photosensors 25 aof residual image area 76 to receive sufficient illumination to form animage. Accordingly, the second capture time used to obtain images fromimage sensor 24 is typically sufficient to form an image on the residualimage area 76 of the image sensor 24 when light from the scene is withina second exposure range 96.

As is shown in FIG. 6C, when the micro-lenses 72 of micro-lens array 12are exposed to light within second exposure range 96, a second exposuresuitable for producing an image i.e. within the actual photosensorlatitude 82 is formed on photosensors 25 a in the residual image area76. In this way, image sensor 24 can be used to record differentiableimages at exposure levels that are above the upper response threshold 86of photosensors 25 of image sensor 24 but below a desired system upperresponse threshold 92.

A region of overlap can be defined between first exposure range 94 andsecond range of scene exposure levels 96. Where it is desired to greatlyincrease system latitude 88, this region of overlap can be contracted.In one embodiment, the ability to capture image information fromphotosensors 25 within either concentrated image areas 74 or residualimage areas 76 over a desired system latitude 88 is ensured by defininga substantial range of exposures wherein first exposure range 94 andsecond exposure range 96 overlap. Alternatively, it may be preferred toprovide an imaging system 4 wherein there is substantial separationbetween first exposure range 94 and second exposure range 96. An imagingsystem 4 having such a substantial separation would effectively operateto capture different images under very different imaging conditions suchas daylight and interior light.

As is shown in FIGS. 6b and 6 c, micro-lens array 12 has a plurality ofmicro-lenses 72 each confronting more than one of photosensors 25. Itwill be appreciated that the fraction of photosensors 25 b receivingmicro-lens focussed light, to enable image capture in first range ofscene exposure levels 94 and the other fraction receiving effectivelyfiltering light, to enable image capture in second range of sceneexposure levels 96light will influence the portion of the image that isshifted in exposure space as discussed in detail in relation to FIGS.6A, 6B and 6C above. The ratio of exposure enhanced photosensors 25 b toother photosensors 25 a is related to the magnitude of the overallshifts in exposure space. This proportion will also influence theresolution and overall image structure capabilities in each exposureregion.

In one embodiment, the ratio of the number of photosensors 25 to thenumber of micro-lenses 72 is at least 1.5 to 1. In another embodiment,the ratio can be at least 2 to 1. In further embodiments the ratio canbe at least 5 to 1, and at least 9 to 1. Additionally, in one embodimentthe ratio of the number of photosensors 25 to the number of micro-lenses72 can be no greater than 1000 to 1. In another embodiment, this ratiois no greater than 100 to 1. In still another embodiment, this ratio canbe no greater than 5 to 1. Further, the structure of micro-lens array 12and the dimensions of micro-lens 72 relative to the layout of imagesensor 24 can be such that the exposure of some individual photosensorsites 25 are not influenced by micro-lenses 72. This embodiment providesa proportion of photosensors 25 that are not shifted in exposure space,thereby preserving latitude 82. In a useful embodiment, the fraction ofphotosensors 25 b positioned to receive focused light on exposure andthe fraction of other photosensors 25 b positioned to receive residuallight on exposure constitute at least 25% of photosensors 25 on imagesensor 24. In a preferred embodiment, the fraction of photosensors 25 bpositioned to receive focused light on exposure and the fraction ofphotosensors 25 a positioned to receive residual light on exposureconstitute at least 50% of photosensors 25 on image sensor 24. While inanother embodiment, the fraction of photosensors 25 b positioned toreceive focused light on exposure and the fraction of other photosensors25 a positioned to receive residual light on exposure constitute atleast 75% of all the photosensors.

It will be appreciated that when an exposure level is in second exposurerange 96 and the first exposure range 94 and second exposure range 96 atleast partially overlap, photosensors 25 b may also contain usefulimaging information. Under these circumstances image information can beobtained from photosensors 25 b. However, where the exposure is abovethe first exposure range 94 then photosensors 25 b in concentrated imageareas 74 will be fully exposed and will not contain any differentiableimage information.

It will be further appreciated that while this discussion has beenframed in terms of a specific embodiment directed towards image captureintended for capturing human visible scenes, the invention can bereadily applied to capture extended scene luminance ranges and spectralregions invisible to humans and the solid state image sensor can be anysolid state image known to the art that has the requisite imagingcharacteristics. The effective increase in latitude enabled can be atleast 0.15 log E. In certain embodiments, the effective increase inlatitude can be between at least 0.3 log E and 0.6 log E. In otherembodiments, the effective increase in latitude is at least 0.9 log E.

FIG. 7A schematically illustrates a face view of another embodiment of amicro-lens array 12 and an associated image sensor 24 is shown. Here anarray 100 of sensitivity enhancing micro-lenses 102 is provided toreduce the amount of light that is allowed to strike light inactiveareas 27. Array 100 positions each sensitivity enhances micro-lens 102in association with one photosensor 25. The optional array 100 is knownin the art.

As can be seen in this embodiment, sensor 24 comprises both a micro-lensarray 12 of dynamic range enhancement micro-lenses 72 and an array 100of sensitivity enhancing micro-lenses 102 as described in U.S. Pat. No.4,667,092 entitled Solid-State Image Device With Resin Lens and ResinContact Layer filed by Ishihara on Dec. 22, 1993. FIG. 7B schematicallyillustrates a side view of the embodiment of FIG. 7A. As is shown inFIGS. 7A and 7B sensitivity enhancing micro-lenses 102 enhance theresponse of each photosensors 25 by concentrating light 106 at theindividual photosensors 25. The larger micro-lenses 72, however, act toconcentrate light 108 at specific ones of the sensitivity enhancingmicro-lenses 102 and associated photosensors 25 b, in concentrated imagearea 74 while allowing residual light to fall onto other ones of themicro-lenses 102 and associated photosensors 25 a, in residual imageareas 76 thereby increasing the luminance range recording capability ofimage sensor 24. Thus, in this embodiment, the sensitivity of allphotosensors 25 is enhanced by micro-lenses 102 while micro-lens array12 of micro-lenses 72 enhances the effective sensitivity of selectedphotosensors 25 b and reduces the effective sensitivity of otherphotosensors 25 a. Digital signal processor 40 can form images usingimage information from photosensors 25 b, so that second image capturesystem 20 can achieve a greater effective sensitivity, than second imagecapture system 20 will have using image information from photosensors 25having their sensitivity enhanced only by a sensitivity enhanced array100 of micro-lenses 102. Digital signal processor 40 can also formimages using image information from both photosensors 25 a and 25 b toachieve a greater effective dynamic range.

In the embodiments described above, micro-lens array 12 has been shownas comprising a cubic, close packed arrangement of circular dynamicrange enhancement micro-lenses 72. This arrangement results in theconcentration of light in the manner described above. In thisembodiment, micro-lenses 72 can have a uniform cross-sectional area.FIG. 8A shows, conceptually, micro-lens array 12 of micro-lenses 72arranged in this uniform cubic close packed distribution pattern by asupport 78. It will be appreciated that other array patterns can beused. For example, FIG. 8B shows an embodiment of micro-lens array 12having an off-set square close packed array pattern. In anotherembodiment shown in FIG. 8C dynamic range enhancement micro-lenses 72are arranged in a micro-lens array 12 having a hexagonal close packedarray pattern. Micro-lens array 12 can also feature random distributionsof dynamic range enhancement micro-lenses 72. One embodiment of an arrayhaving a random distribution is shown in FIG. 8D. As is shown in FIG.8E, in still another embodiment, array 12 can comprise an array ofcylindrical or acylindrical dynamic range enhancement micro-lenses 72.

As is shown in FIGS. 9A, 9B and 9C, micro-lens array 12 can comprisedynamic range enhancement micro-lenses 72 having different opticalcharacteristics. In the embodiment of FIG. 9A, micro-lens array 12 ofcylindrical dynamic range enhancement micro-lenses 72 is shown. As isshown in FIG. 9A, micro-lens array 12 has a first set of micro-lenses 72a that have a greater cross-section area than a second set ofmicro-lenses 72 b also provided by micro-lens array 12. In thisembodiment, the first set of micro-lenses 72 a concentrate a greaterportion of light during an exposure than micro-lenses 72 b. Thus, thefirst set of micro-lenses 72 a form a line image exposure 75 a on imagesensor 24 as shown in FIG. 9D, in a first set of concentrated imageareas 74, when the amount of the light during the exposure is within afirst exposure range 84. When light from the scene is within a secondexposure range 86, the second set of micro-lenses 72 b form a line imageexposure 75 b on image sensor 24 in a second set of concentrated imageareas 74 b. Light that is not concentrated by either set of micro-lenses72 a and 72 b can form a residual image (not shown) in residual imagearea 76 of image sensor 24 of FIG. 9D. Similarly, FIGS. 9B and 9C eachshow the use of a micro-lens array 12 having differently sized sets offirst set of micro-lenses 72 a and second set of micro-lenses 72 b withmicro-lens array 12 concentrating light and directing that light ontoconcentrated image areas 74 a to form line image exposure 75 a whenlight from the scene is within a first range. Micro-lenses 72 bconcentrate light from a scene and direct this light onto concentratedimage areas 74 b to form a line image exposure 75 b when the light fromthe scene is within a second range. Here too, residual portions of thelight are recorded in residual image areas 76. Thus, in theseembodiments of FIGS. 9A-9C the effective latitude of image sensor 24 canbe further extended.

As is shown in FIG. 9C, the surface coverage of micro-lenses 72 does nothave to be maximized. While any useful surface coverage of micro-lenses72 can be employed, the ratio of the projected area of micro-lenses 72to area of image sensor 24 occupied by the photosensors 25 can be atleast 5 percent.

In one embodiment, the coverage can be between at least 50 percent andup to 85 percent. In another embodiment, surface coverage of 85 percentup to the close-packed limit can be used. The precise degree of surfacecoverage can be adjusted to enable varying levels of exposure latitudewhile maintaining useful image quality. In any embodiment where thesurface coverage is less than the close packed limit, support 78 can bedefined to allow residual light to pass to image sensor 24.

It will be appreciated that the concentration of light by micro-lensarray 12 of dynamic range enhancement micro-lenses 72 also performs theoptical equivalent of re-sampling the image formed on an imaging surfacesuch as second imaging surface 21 of second image capture system 20.Accordingly, in one useful embodiment of the present invention, thesurface coverage of micro-lens array 12 can be matched to correspond tothe imaging resolution of a display such as viewfinder display 33 orexterior display 42 in imaging system 4 and micro-lens array 12 can beplaced in optical association with imaging surface 21 such as on imagesensor 24. Where this is done, an evaluation image can be extracted fromimage sensor 24 at an image resolution appropriate for display simply byscanning extracted image data from the image sensor and assembling imageinformation only from the concentrated image areas. This speeds imageprocessing by eliminating the need for digital signal processor 40 toperform the step of resampling an initial image so that an evaluationimage can be provided more quickly. Further, micro-lens array 12 can beused to direct concentrated light onto particular sections of imagesensor 24. This permits image sensor 24 to have photosensors 25 that areinoperative to be used to capture evaluation images in that micro-lensescan be used to concentrate light away from inoperative photosensors andonto adjacent operative photosensors without impairing image quality.Accordingly, lower cost imagers can be used.

It will also be appreciated that the dynamic range of an imaging surfacesuch as first imaging surface 11 can vary during operation of theimaging system. For example, in the embodiment of FIG. 1 first imagingsurface 11 is located on photosensitive element 14 which can, forexample, comprise a film. Where different films are loaded into firstimage capture system 10, the sensitivity of the films can vary as isindicated by speed ratings for the films. The micro-lens array 12 can beprovided with different types of micro-lenses 72 adapted to concentratelight in different intensities to form separate concentrated andresidual images on an imaging surface. These different types ofmicro-lenses can be adapted to record images on second imaging surface21 that generally correspond to the dynamic ranges of various types offilms that can be located in an imaging system or that coincide with,for example 60% of the dynamic range of the films. In this way, whenmicroprocessor 50 determines that a photosensitive element in imagingsystem 4 is rated at one speed, microprocessor 50 can cause digitalsignal processor 40 to extract an image using photosensors formed bymicro-lenses that concentrate light in a way that is intended to providea dynamic range that corresponds to the dynamic range of aphotosensitive element 14.

Micro-lens array 12 can comprise a set of individual micro-lenses 72that are formed together or joined together, for example by extrusion,injection molding and other conventional fabrication techniques known tothose in the art. Micro-lens array 12 can also be formed by combining aplurality of separate micro-lenses 72 fixed together by mechanical orchemical means or by mounting on support 78. Micro-lens array 12 cancomprise a set of lenticular beads or spheres (not shown) that arepositioned proximate to or coated onto image sensor 24 or otherwisejoined to image sensor 24. Micro-lenses 72 may be formed in any matterknown in the microstructure art. Micro-lenses 72 may be unitary withimage sensor 24, as for example by being embossed directly into imagesensor 24 at manufacture or they may be integral to a distinct layerapplied to image sensor 24. In still other embodiments, a micro-lensarray 12 can be formed using a photosensitive coating.

The dimensions of imaging system 4 and the detailed characteristics ofthe taking lens unit 6 dictate the exposure pupil to image distance,i.e. the camera focal length. Preferably, an image is formed at thearray of micro-lenses 12. The characteristics of micro-lenses 72 dictatetheir focal length. The micro-lens images are formed at the lightsensitive areas of image sensor 24. The f-number of taking lens unit 6controls the depth-of-focus and depth-of-field of imaging system 4 whilethe micro-lens f-number controls the effective aperture of imagingsystem 4. By using taking lens unit 6 having a stopped down f-number,excellent sharpness along with wide depth of focus and depth of fieldare obtained. By using an opened f-number for micro-lens array 72, highsystem speed is obtained.

Accordingly, a useful combination of taking lens unit 6 and micro-lenses72 f-numbers will be those that enable system speed gains. System speedgains of more than 0.15 log E, or ½-stop, are useful, while system speedgains 0.5 log E or more are preferred. While any micro-lenses 72 havingan f-number that enables a speed gain with taking lens unit 6 havingadequate depth-of-field for an intended purpose can be gainfullyemployed, typically micro-lenses 72 having f-numbers of 1.5 to 16 areuseful. In certain embodiments, micro-lenses 72 having f-numbers in therange of f/2 to f/7 are useful. In other embodiments, micro-lenses 72having f-numbers in the range of f/3 to f/6 are preferred.

The individual micro-lenses 72 are convergent lenses in that they areshaped so as to cause light to converge or be focused. As such, theyform convex projections from the support 78. The individual projectionsare shaped as portions of perfect or imperfect spheres. Accordingly,micro-lenses 72 can be spherical portion lenses or they can beaspherical portion lenses. Both types of micro-lenses can besimultaneously employed. A spherical portion micro-lens 72 has the shapeand cross-section of a portion of a sphere. An aspherical portionmicro-lens 72 has a shape and cross-section of a flattened or elongatedsphere. The lenses arc micro in the sense that they have a circular ornearly circular projection. Any useful lens diameter consistent with theoperation of the invention as described and the dimensions of knownsolid state imager arrays can be usefully employed. In one embodiment,micro-lenses 72 with a diameter of between 1 and 1000 microns are used.A cylindrical portion micro-lens 72 has the shape and cross-section of aportion of a cylinder. An acylindrical portion micro-lens 72 has a shapeand cross-section of a flattened or elongated cylinder. FIGS. 10A-10Dshow a cross-sectional view of micro-lenses 72 mounted in a support 78and exhibiting example embodiments of various spherical and asphericalmicro-lenses 72.

FIG. 10A shows an embodiment wherein micro-lenses 72 comprise sphericallenses joined by support 78. FIGS. 10B and 10C show embodiments ofmicro-lens array 12 having aspherical micro-lenses 72. It is appreciatedthat any of the above described array patterns may be combined withaspherical micro-lenses 72 to provide extended latitude. Further, any ofthe patterns of micro-lenses 72 can be applied in a non-close packedmanner to enable extended photographic latitude.

Micro-lenses 72 are shown with distinct hatching to illustrate thespherical and aspherical character of the protruding portion thatactually forms the micro-lens. Aspherical micro-lenses 72, of the typeshown in FIGS. 10B and 10C, are especially useful for this applicationin that the variable radius of such lenses allows for control of thelens focal length and lens aperture nearly independently of the spacingbetween micro-lenses 72 and photosensors 25. While these cross-sectionshave been described as spherical or aspherical, it is fully appreciatedthat the diagrams equally represent in cross-section cylindrical oracylindrical micro-lenses 72.

The light concentration or useful photographic speed gain onconcentrating light focused by taking lens unit 6 with a circularprojection micro-lens 72 is the square of the ratio f-numbers of imagingsystem 4 and the micro-lenses 72. Speed gain (in log relative Exposure)in such a system can be determined as the speed gain equals 2×log(camera lens f-numbers/micro-lens f-numbers). The light concentration oruseful photographic speed gain of cylindrical micro-lenses 72 allow thesquare root of such an improvement because they concentrate light inonly one direction. The concentration of light by micro-lens array 12enables both a system speed gain and forms an exposure pattern imagesensor 24.

Preferred design parameters for micro-lenses 72 and their relationshipto photosensors 25 of image sensor 24 follow from these definitions:

Micro-lens radius is the radius of curvature of the hemisphericprotrusion of micro-lenses 72. For aspherical micro-lenses 72 this valuevaries across the surface of the micro-lens.

Micro-lens aperture is the cross sectional area formed by the micro-lenstypically described as a diameter. For spherical micro-lenses thisdiameter is perforce less than or equal to twice the micro-lens radius.For aspherical micro-lenses this diameter can be greater than twice thesmallest radius encountered in the micro-lens. Use of differently sizedmicro-lenses having distinct apertures enables distinct levels of speedgain on a micro-scale and thus enables extended exposure latitude for aphotosensitive site.

Micro-lens focal length is the distance from micro-lenses 72 tophotosensors 25 of image sensor 24.

Micro-lens f-number is the micro-lenses 72 aperture divided by themicro-lens focal-length. For spherical micro-lenses 72, the desiredmicro-lens focal length can be used to define an appropriate micro-lensradius following a lens equation, thusly:

Micro-lens radius is the micro-lens focal-length times (n₂−n₁)/n₂; wheren₁ is the refractive index of the material outside the micro-lens(typically air with a refractive index of unity) while n₂ is therefractive index of the micro-lens and any contiguous transmissivematerial e.g. (plastics as used in array support 78.) The usefulplastics or polymers typically have a refractive index of 1.4 to 1.7).The ratio of the highest to the lowest refractive index can be between0.8 and 1.2. In preferred embodiments the ratio is between 0.95 and1.05. Following the known refractive indices of typical photographicsystem components, useful spherical micro-lenses will have a micro-lensfocal length about 3 times the micro-lens radius ((n₂−n₁)/n₂˜⅓).Non-integral micro-lenses 72 can be made from a wider variety ofplastics and glasses. For micro-lenses 72 that are integrally formed onimage sensor 24, superior optical properties are provided when therefractive index of the materials used to form the composite opticaldevice are as similar as possible.

FIG. 11 shows a flow chart of a method for capturing an image accordingto the invention. As is shown in FIG. 11, the process begins when ashutter trigger button 60 is depressed by user 5 causing a triggersignal to be generated (step 120). Microprocessor 50 detects the triggersignal indicating that shutter trigger button 60 has been depressed andcauses first image capture system 10 and second image capture system 20to capture images. A sensor exposure step is executed (step 122) usingsecond imaging system 20 and image sensor 24 as described above. Thearray of micro-lenses 12 reduces range enhancing of scene informationinto concentrated image areas 74 and residual image area 76. Sensor 124is interrogated (step 124) to capture and fix the exposure information.In this embodiment, image information is extracted from photosensors 25b within the concentrated image areas 47 (step 126). Image informationis also extracted from the photosensors 25 a in the residual image area76 (step 128). The extracted image information is reconstructed (step130) to form a likeness of the original scene.

Under low exposure conditions, scene information is determined basedupon image conditions in the photosensors 25 b in concentrated imagearea 74. In one embodiment, photosensors 25 b in concentrated image area74 are separated from photosensors 25 a in residual image area 76 duringa calibration process so that digital image processor 40 can quickly andefficiently separate image information obtained from concentrated imagearea 74 and residual image area 76. Alternatively, a single image can beobtained from image sensor 24 and processed by digital signal processor40 which then uses image analysis techniques to separate imageinformation obtained from concentrated image area 74 and imageinformation obtained from residual image area 76.

Under high exposure conditions, scene information is carried inphotosensors 25 a in residual image areas 76. FIG. 12 shows a contrastpattern image formed on image sensor 24 after image wise exposure ofimage sensor 24 to light from a scene that is within a first range ofscene exposure levels 94. As is discussed above, when imaging system 4is exposed to first range of exposure levels 94 image information isdirectly recorded by photosensors 25 a in residual image areas 76 in theform of a residual image 104. Residual image 104 is similar to the imageformed by conventional optical imaging techniques. However, as is shownin FIG. 12, residual image 104 is not a continuous image in that imaginginformation useful in the composition of residual image 104 is lostduring the concentration of light onto photosensors 25 b. There arevarious methods by which this information can be corrected. For example,interpolation techniques can be used to compensate for the missinginformation. In certain applications, under sampling techniques can beused to process imaging information captured by photosensors 25 a.

Alternatively, where exposure conditions in the scene overlap, sceneinformation can be obtained from photosensors 25 a and 25 b. Further, itwill be appreciated that exposure conditions can vary within an imageand, therefore, where a scene contains a wide range of exposure levels,it can occur that the exposure level in one portion of the image will bewithin the first exposure range 94 while the exposure level in thesecond portion of the same image will be in the second exposure range96. Thus, in such an image, part of the image information will beobtained from photosensors 25 b in the concentrated image areas 74 whileanother part of the image information will be obtained from photosensors25 a in residual image areas 76. Where this occurs, a single outputimage is composed by assembling the output image using image informationfor both concentrated image areas 72 and residual image areas 74 Animage formed in this manner will contain imaging informationrepresentative of a scene exposure over a dynamic range that includesthe entire desired system latitude 88.

It is appreciated that the forgoing discussion is couched in termsspecific to system sensitivity enhancement enabled by the use ofmicro-lens array 12 as applied to image sensors such as solid statesensors. Although the underlying mechanistic considerations are somewhatdistinct, similar considerations apply to sensitivity enhancementenabled by the use of intervening micro-lens array 12 as can be appliedto photosensitive elements 14 such as photosensitive silver halidefilms. With silver halide films, the lower response threshold is set byconsideration of the minimal applied photon flux required to make asilver halide grain developable, while the upper response threshold isset by either exhaustion of the density forming ability of the film orby full exposure of individual incorporated silver halide grains. When aphotosensitive element 14 is optically associated with micro-lens array12, image formation is accomplished by a photoprocessing developmentstep with optional desilvering and stabilizing as known in the artfollowed by direct optical printing or scanning and digitization usingtechniques described in the commonly assigned and cross-referencedpatent applications.

FIG. 13 schematically illustrates another embodiment of an imagingsystem 4 having a first image capture system 10 comprising an imagecapture system for capturing images on a photosensitive element 14 andwith a second image capture system 20 that captures images using animage capture sensor 24. Here, the imaging system 4 comprises a beamsplitter 8, and a micro-lens array 12 having individual micro-lenses 72positioned at the focal plane of the micro-lens array 12. On exposure,image light strikes beam splitter 8 and a portion of the light is passedto the first imaging surface 11 to expose photosensitive element 14,while the balance of the light is passed to the second imaging surface21 to expose image sensor 24.

In the embodiment shown in FIG. 13, shutter system 23 modulates thepassage of light from the scene to beam splitter 8 thus controllingexposure of both the light photosensitive clement 14 and the imagesensor 24. As is shown in this embodiment, micro-lens array 12 a isprovided for image capture system 10, while a second micro-lens array 12b is provided for second image capture system 20. Micro-lens array 12 ais arranged with micro-lenses arranged in an inverse mountedarrangement, with each micro-lens 72 having a light receiving surface140 to receive light from beam splitter 8 and a light focusing surface142 confronting photosensitive element 14. Light focusing surface 142 isadapted to concentrate the received light onto photosensitive element14. Spacer 144 positions photosensitive element 14 separate from thelight focusing surfaces 142. The spacer can, for example, comprise anystructure that is capable of providing a separation between lightfocusing surfaces 142 and photosensitive element 14. This arrangement isuseful with an array of micro-lenses 12 b having very fine pitch.

The individual micro-lenses 72 of array 12 a and the surrounding medium,define a focal plane offset from the focusing surface of themicro-lenses 72. When imaging system 4 is loaded with light sensitivesilver halide film 14, film 14 is positioned and aligned by film gatesystem 15 at the focal plane defined by the individual micro-lenses 72and the surrounding medium.

In the aforesaid embodiments, the light sensitive film imaging systemhas been described as optionally employing a distinct micro-lens array.Other embodiments employing light sensitive films with emulsion sidemicro-lenses, with base side micro-lenses and with micro-lenses formedby partially embedded beads are specifically contemplated.

In another embodiment, a micro-lens array 12 assembly can be augmentedby stacked array magnifier as described by U.S. Pat. No. 6,381,072entitled Lenslet Array Systems And Methods, PCT filed by Burger on Jan.23, 1998, to adjust image frame size as desired for particularapplications. In this context, the stacked array magnifier enables theuser optional use of multiple format films, i.e. films having distinctslit widths or frame sizes in one of the imaging systems. Further, thestacked array magnifier enables the user optional use of a film of oneframe size in an imaging system in place of a solid state imager withoutnecessity of grossly altering the optical properties of the camera. Aspecific embodiment is a camera with a first film based imaging systemresponsive to human visible images and a second imaging system that useroptionally employs a solid state imager or a film imaging systemresponsive to human non-visible light, as in a security or observationcamera.

Further details regarding the use of an array of micro-lenses 8 toimprove image capture capacity regarding micro-lens reconstruction alongwith micro-lens sizing, shape and optical properties are disclosed inU.S. appl. Ser. No. 10/167,794, entitled “Imaging Using Silver HalideFilms With Micro-Lens Capture And Optical Reconstruction,” filed in thename of Irving et al. on Jun. 12, 2002 and U.S. appl. Ser. No.10/170,148 entitled “Imaging Using Silver Halide Films With Micro-LensCapture, Scanning And Digital Reconstruction,” filed in the name ofSzajewski et al. on Jun. 12, 2002, the disclosures of which areincorporated by reference. The combination of micro-lens arrays withsolid state image capture devices are described in U.S. appl. Ser. No.10/326,455 entitled “Digital Camera Having Extended Useful Latitude”filed in the name of Szajewski et al. on Dec. 20, 2002, and U.S. appl.Ser. No. 10/281,654 entitled “Inverse Mounted Micro-Lenses,” ofSzajewski et al., the disclosures of which are incorporated byreference.

In another embodiment, the first image capture system 10 and the secondimage capture system 20 can both capture images on photosensitiveelement 14 that can be used in combination with beam splitters 12, forexample, to enable color separation exposures. Here, color filters canbe used with pan sensitized photosensitive elements. Alternatively, thephotosensitive elements can be specifically sensitized to the desiredcolor sensitivity as known in the art. In yet another embodiment, two ormore solid state image capture systems can be employed with separateimagers used in combination with multiple beam splitters to enable colorseparation exposures. The, color filters can be used to enable colorspecific image capture. The sensitivities can be the human visible red,green and blue triad, the complementary cyan, magenta yellow triad orcan include UV, IR or far IR sensitivities as desired for specificapplications.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it will be understood thatvariations and modifications can be effected within the spirit and scopeof the invention.

PARTS LIST

4 imaging system

5 user

6 taking lens unit

8 beam splitter

10 first image capture system

11 first imaging surface

12 micro-lens array

12 a micro-lens array

12 b micro-lens array

13 photosensitive element positioning system

14 photosensitive element

15 gate system

16 film supply system

17 pressure plate

18 photosensitive element contact surface

19 pressure plate assembly

20 second image capture system

21 second imaging surface

23 shutter system

24 image sensor

24 photosensors

25 a photosensors in a residual image area

25 b photosensors in a concentrated image area

26 element

27 inactive areas

28 element

30 lens driver

32 viewfinder system

33 viewfinder display

34 analog signal processor

35 viewfinder optics

36 A/D converter

38 frame memory

39 display driver

40 digital signal processor

42 exterior display

44 data memory

46 communication module

48 rangefinder

50 microprocessor

52 memory card

54 memory card slot

56 memory card interface

58 user controls

60 shutter trigger button

62 “wide” zoom lens button

63 accept button

64 “tele” zoom lens button

66 timing generator

68 sensor driver

72 dynamic range enhancement micro-lens

72 a first set of micro-lens

72 b second set of micro-lens

74 concentrated image area

74 a first set of concentrated image areas

74 b second set of concentrated image areas

75 a line image exposure

75 b line image exposure

76 residual image area

78 support

80 scene luminance range

82 actual photosensor latitude

84 lower response threshold

86 upper response threshold

88 desired system latitude

90 desired system lower response threshold

92 desired system upper response threshold

94 first range of scene exposure levels

96 second range of scene exposure levels

100 array of sensitivity enhancing micro-lenses

102 sensitivity enhancing micro-lenses

104 residual image

106 sensitivity enhancing concentrated light

108 concentrated light

120 detect trigger signal step

122 execute sensor exposure step

124 interrogate sensor step

126 extract image information from photosensors in concentrated imagearea step

128 extract image information from photosensors in residual image area

130 reconstruct image step

140 light receiving surface

142 light focusing surface

144 spacer

A first axis

B Second axis

What is claimed is:
 1. An imaging system comprising: a taking lens unitadapted to focus light from a scene; a beam splitter receiving lightfrom the scene with a portion of the received light traveling from thebeam splitter to a first imaging surface and a portion of the receivedlight traveling from the beam splitter to a second imaging surface; afirst image capture system for capturing an image based upon the lighttraveling to the first imaging surface; a second image capture systemfor capturing a second image based upon the image formed at the secondimaging surface; and an array of micro-lenses in optical associationwith the second imaging surface, with each micro-lens in the arrayconcentrating a first fraction of the light from the beam splitter ontoconcentrated image areas of the second imaging surface; wherein thesecond image capture system forms an image based upon the lightconcentrated onto the concentrated image areas.
 2. The imaging system ofclaim 1, wherein the array of micro-lenses also permits a secondfraction of the light to form a residual image in areas of theassociated imaging surface that surround the concentrated image areas.3. The imaging system of claim 2, wherein the array of micro-lensesconcentrates the first fraction of the light to form an image in theconcentrated image areas of the second imaging surface when light fromthe scene is within a first range of exposure and wherein the secondfraction of the light from the beam splitter forms an image in aresidual image area surrounding the concentrated image areas of thesecond imaging surface when light from the scene is within a second,higher, range of exposures.
 4. The imaging system of claim 3, whereinthe second image capture system forms an image based upon the pattern ofconcentrated image elements and the image formed in the residual imagearea.
 5. The imaging system of claim 4, wherein the first image capturesystem captures an image when light from the scene is within a thirdrange of exposures, and wherein micro-lenses are selected so that thefirst range of exposures and the second range of exposures generallycoincide with the third range of exposures.
 6. The imaging system ofclaim 4, wherein the first image capture system captures an image whenlight from the scene is within a third range of exposures, and whereinmicro-lenses are selected so that the first range of exposures and thesecond range of exposures coincide with at least 60% of the third rangeof exposures.
 7. The imaging system of claim 1, wherein the micro-lensesconcentrate light so that the appearance of the image captured by thesecond image capture system based upon the pattern of concentrated lightgenerally corresponds to the appearance of the image captured by thefirst image capture system.
 8. The imaging system of claim 1, whereinthe micro-lenses concentrate light so that the second image capturesystem can capture images when the scene illumination is above a firstlower response threshold and wherein the first image capture system isadapted to capture images when the scene illumination is at least abovea second lower response threshold with the first lower responsethreshold being at least as low as the second lower response threshold.9. The imaging system of claim 8, wherein first image capture system andsecond image capture system are optically associated with, respectively,a first array of micro-lenses and a second array of micro-lenses thatare adapted so that the first image capture system and second imagecapture system are capable of capturing similar appearing images of ascene when exposed to a scene having a predefined range of illuminationintensities.
 10. The imaging system of claim 1, wherein a second arrayof micro-lenses is optically associated with the first image capturesystem, with each micro-lens in the second array concentrating a firstfraction of the light traveling to the first imaging surface ontoconcentrated image areas of the first imaging surface and wherein thesecond image capture system forms an image based upon the concentratedimage areas.
 11. The imaging system of claim 1, wherein the fraction oflight traveling to the second imaging surface is less than the fractionof light traveling to the first imaging surface.
 12. The imaging systemof claim 1, wherein the fraction of the light traveling to the secondimaging surface is between 5%-95% of the light received by the beamsplitter.
 13. The imaging system of claim 1, wherein the beam splittercomprises at least one of a prism or a mirror.
 14. The imaging system ofclaim 1, wherein the second imaging surface comprises an image sensorand the second image capture system comprises a processor and a display,wherein the processor collects image information from the image sensor,processes the image information and presents the images captured by thesecond image capture system on the display.
 15. The imaging system ofclaim 14, wherein the display has a predefined display resolution thatis less than an imaging resolution of the first imaging sensor and thearray micro-lenses comprises an array of micro-lenses that concentrateslight to form a pattern of concentrated image elements on the imagesensor that corresponds to the display resolution of the display. 16.The imaging system of claim 1, wherein the second imaging surfacecomprises an image sensor having a plurality of photosensitivephotosites and wherein there are fewer micro-lenses in the array ofmicro-lenses than there are photosites in the plurality of image sensingphotosites.
 17. The imaging system of claim 1, wherein the secondimaging surface comprises an image sensor having an array of spacedphotosensor areas and wherein each micro-lens in the array ofmicro-lenses receives light directed at more than one of thephotosensors and concentrates a portion of the received light onto lessthan all of the photosensors at which the received light is directed.18. The imaging system of claim 1, wherein the first imaging surface andthe second imaging surface comprise image sensors that use photosensorsto convert incident light into electrical charge.
 19. The imaging systemof claim 1, wherein at least one of the imaging surfaces comprises aphotosensitive element having chemicals generate a latent image whenexposed to light.
 20. An image capture system comprising: a taking lensunit adapted to focus light toward a beam splitter with the beamsplitter receiving light from the taking lens unit and passing a portionof light to form an image at a first imaging surface and a portion ofthe light to form an image at a second imaging surface; a photosensitiveelement image capture system having a shutter assembly for controllingthe passage of light to at least one imaging surface and aphotosensitive element positioning system having gate positioning aphotosensitive element having the first imaging surface thereon toreceive light controlled by the shutter assembly; an electronic imagecapture system having an image sensor with the second imaging surfacethereon said electronic image capture system adapted to capture an imagebased upon the light incident on the second imaging surface; amicro-lens array in optical association with the second imaging surfaceimaging plane concentrating light directed at concentrated image areasof the second imaging surface; and a controller for determining acapture time and for enabling the shutter assembly and electronic imagecapture system to capture an image representative of scene conditionsduring the capture time.
 21. The image capture system of claim 20wherein the shutter assembly is positioned so that the shutter controlsthe passage of light to every imaging surface.
 22. The image capturesystem of claim 21 wherein the array of micro-lenses opticallydownsamples the image.
 23. The image capture system of claim 21 whereinthe controller determines a sensitivity for the photosensitive element,determines a capture time and causes the shutter assembly to open forthe capture time and further causes the electronic image to capture animage based upon the scene conditions during the capture time.
 24. Theimage capture system of claim 21, wherein the controller determines asensitivity for the photosensitive element, determines a desiredeffective sensitivity for the photosensitive element image capturesystem based at least in part upon the sensitivity of the photosensitiveelement, and further causes the electronic image capture system tocapture images in a manner that has an effective sensitivity thatcorresponds to the effective sensitivity of the photosensitive elementimage capture system.
 25. The image capture system of claim 21 whereinthe photosensitive element image capture system is adapted to receive aset of different types of photosensitive elements with each type ofphotosensitive element in the set having a different sensitivity,wherein the array of micro-lenses comprises an array having a set ofdifferent types of micro-lenses with each type of micro-lensconcentrating light in a manner adapted to correspond to one type of thephotosensitive elements so that the sensitivity of each different one ofthe photosensitive elements in the set can be matched by selectivelyforming an image based upon the light concentrated by the set ofmicro-lenses corresponding to a particular photosensitive element. 26.The image capture system of claim 25 wherein the processor is adapted todetermine the sensitivity of a photosensitive element and to cause theelectronic image capture system to capture images based upon lightconcentrated by micro-lenses that are associated with the type ofmicro-lens associated with the sensitivity of the photosensitiveelement.
 27. The image capture system of claim 21 wherein the electronicimage capture system begins an image capture sequence only when lightfrom the scene strikes the image sensor.
 28. The image capture system ofclaim 20 wherein the electronic image capture system incorporates adisplay and the electronic image capture system processes the capturedimage for presentation on the display.
 29. The image capture system ofclaim 28, wherein the electronic image capture system resamples thecaptured image for presentation on the display.
 30. The image capturesystem of claim 29, wherein the electronic image capture systemincorporates a display and the electronic image capture system processesthe captured image into a form that has an appearance that is adapted togenerally correspond to the appearance of the image captured on thephotosensitive element.
 31. The imaging system of claim 28, wherein thedisplay has a predefined display resolution that is less than an imagingresolution of the first imaging sensor and the array micro-lensescomprises an array of micro-lenses that concentrates light to form apattern of concentrated image elements on the first imaging sensor withthe pattern having a number of concentrated image elements thatcorresponds to the number of display elements.
 32. The imaging system ofclaim 20, wherein the micro-lens array also permits a residual image ofnon-concentrated light to be formed on residual areas of the secondimaging surface with the electronic image capture system comprising: adisplay processor adapted to collect image information from concentratedimages areas and from residual image areas of the image sensor toprocess the image information to form a captured image and to presentthe captured image on the display.
 33. An imaging system comprising: ataking lens unit adapted to focus light from a scene; an image capturesystem for capturing an image based upon the light traveling to animaging surface; a stacked array magnifier positioned to alter theeffective magnification of the light traveling to the imaging surface;and an array of micro-lenses in optical association with the imagingsurface, with each micro-lens in the array concentrating a firstfraction of the light onto concentrated image areas of the imagingsurface; wherein the image capture system forms an image based upon thelight concentrated onto the concentrated image areas.
 34. A method forcapturing an image of a scene using a first imaging surface having afirst sensitivity and a second imaging surface having a secondsensitivity, the method comprising the steps of: focusing light from thescene; dividing the focused light from the scene into a first portiontraveling to a first imaging surface and a second portion traveling to asecond imaging surface; capturing a first image based upon the lightreaching the first imaging surface; concentrating a fraction of thelight traveling to the second imaging surface to form a pattern ofconcentrated image elements on the second imaging surface; and capturinga second image based upon the pattern of concentrated image elementsformed on the second imaging surface.
 35. The method of claim 34 whereina second fraction of the light traveling to the second imaging surfaceis not concentrated and forms a residual image on areas of the firstimaging surface that surround the concentrated image areas.
 36. Themethod of claim 35 wherein the step of concentrating the light travelingto the second imaging surface comprises concentrating the lighttraveling to the second imaging surface so an image that is formed basedupon the pattern of concentrated image elements appears to have beencaptured using an image capture surface having the sensitivity of thefirst image capture surface.
 37. The method of claim 36, wherein thesecond image is formed based upon the pattern of concentrated imageelements and the image formed in the residual image area.
 38. The methodof claim 36, wherein the first image comprises an image formed fromlight the scene that is within a third range of exposures, and whereinlight is concentrated so that the first range of exposures and thesecond range of exposures generally coincide with the third range ofexposures.
 39. The method of claim 36, wherein the first imagescomprises an image formed from light from the scene that is within athird range of exposures, and wherein degree of light concentration isselected so that the first range of exposures and the second range ofexposures coincide with at least 60% of the third range of exposures.40. The method of claim 34 wherein the first fraction of the lighttraveling to the second imaging surface is concentrated to form an imagein the concentrated image areas of the imaging surface when light fromthe scene is within a first range of exposure and wherein a secondfraction of the light traveling to the second imaging surface forms animage in a residual image area surrounding the concentrated image areasof the second imaging surface when light from the scene is within asecond, higher, range of illumination intensities.
 41. The method ofclaim 34, wherein the micro-lenses concentrate light so that theappearance of the image captured by the second image capture systembased upon the pattern of concentrated light generally corresponds tothe appearance of the image captured by the first image capture system.42. The method of claim 34, wherein light traveling to the secondimaging surface is concentrated so that a first image can be capturedusing the concentrated light when the scene illumination is above afirst lower response threshold and wherein the first image is capturedwhen the scene illumination is at least above a second lower responsethreshold, with the first response threshold being at least as low asthe second lower response threshold.
 43. The method of claim 42, whereinthe first image and second image have a similar appearance when exposedto a scene having a predefined range of illumination intensities. 44.The method of claim 34, wherein a fraction of the light traveling to thesecond imaging surface is concentrated onto concentrated image areas ofthe second imaging surface and wherein the second image is based uponthe concentrated fraction of the light.
 45. The method of claim 34,wherein the portion of light traveling to the second imaging surface isless than the portion of light traveling to the first image capturesystem.
 46. The method of claim 34, wherein the portion of the lighttraveling to the second imaging surface is between 5%-95% of the lighttraveling to the second imaging surface.
 47. The method of claim 34,wherein the second imaging surface comprises an electronic image sensorand the step of capturing a first image comprises capturing a secondimage by using the electronic image sensor to covert light incident onthe first imaging surface into electronic signals.
 48. The method ofclaim 47, further comprising the steps of processing the electronicsignals into an image that can be presented on a display and presentingthe image on the display.
 49. The method of claim 48, wherein thedisplay has a predefined display resolution defined by a number ofdisplay elements that is less than an imaging resolution of theelectronic imaging sensor and the light traveling to the second imagingsurface is concentrated to form a pattern of concentrated image elementson the electronic imaging sensor having a number of concentrated imageelements that corresponds to the number of display elements.
 50. Theimaging system of claim 34, wherein the second imaging surface comprisesan image sensor having a plurality of photosensitive photosites andwherein there are fewer micro-lenses in the array of micro-lenses thanthere are photosites in the plurality of image sensing photosites. 51.The method of claim 34, wherein the second imaging surface comprises animage sensor having an array of spaced photosensor areas and whereinlight directed at the second imaging surface at an area containing morethan one of the photosensors is concentrated onto less than all of thephotosensors in the area at which the received light is directed. 52.The method of claim 34, wherein at least one of the steps of forming afirst image and forming a second image comprise forming by convertinglight incident on one of the first and second imaging surfaces intoelectrical charge and processing the electrical charge to form aelectronic signal representing the image.
 53. The method of claim 34,wherein at least one of the imaging surfaces comprises a photosensitiveelement having chemicals that generate a latent image when exposed tolight.